And I'm Audie Cornish. In a cemetery in Beirut, Lebanon, new graves are appearing more frequently than usual. This isn't just any cemetery. It's where the martyrs of Hezbollah are buried. The Shiite militant group is backed by the governments of Iran and Syria. While it's not clear where these latest martyrs were killed, members of Syria's opposition accuse the group of sending fighters into their country to help its embattled government.

NPR's Leila Fadel reports.

LEILA FADEL, BYLINE: A stonemason crafts the latest gravestone of a martyr in the cemetery in a southern suburb of Beirut. All around us are the new and old graves of those who died fighting for Hezbollah. A man grieves over a lost loved one. Shopkeepers in the area say the burials are more frequent now. But Hezbollah, created in 1982 to resist the Israeli invasion of Lebanon, is not at war now, at least not openly.

The question is where are these martyrs dying? That Hezbollah commander was called Ali Hussein Nassif. The group announced his death, saying he died performing his duties of jihad but gave no other details. Activists and rebel commanders in Syria accuse Hezbollah of sending fighters like Nassif to bolster the Assad regime. They say the deaths prove that Hezbollah is active in the Syrian conflict.

Many Lebanese are worried that an intervention in Syria will drag Lebanon into that conflict.

ABU AZZAM: (Foreign language spoken)

FADEL: Abu Azzam, a Syrian rebel commander in Turkey, says he believes the number of Hezbollah fighters in Syria is rising. He says his fighters can recognize them by their Lebanese accents. In the face of the rising accusations, Hezbollah Secretary General Hassan Nasrallah took to the airwaves yesterday.

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HASSAN NASRALLAH: (Through Interpreter) Until this moment, we have not fought alongside the Syrian regime. First of all, the regime has not requested help form us. Secondly, who says this would benefit us or that it's our responsibility?

FADEL: Nasrallah says the only place members of Hezbollah are fighting is in their own villages. He says some 30,000 Lebanese Shiites live in villages that are technically on Syrian territory. They are dealing with attacks by Syrian rebel forces and mines planted near the villages. As for the slain military commander, Nasrallah said he led Hezbollah operations in the eastern Bekaa Valley and was killed in a bombing in a Lebanese village.

Nasrallah says the accusations of Hezbollah involvement in Syria are a smear campaign, and he warned the rebel Free Syrian Army, which is threatening to take the fight to Hezbollah.

NASRALLAH: (Through Interpreter) You are pushing me to make decisions I don't want to make. Leave us out of the battle. And I end this by saying no one can threaten us.

FADEL: Analysts say Hezbollah is walking a delicate line. It has made clear that it does not want the Syrian war to spill over into Lebanon, but it has also voiced its support for the Assad regime just as the leaders of Lebanon's Sunni Muslim community have backed the Syrian rebels. Many Hezbollah supporters accused the Sunni leadership of sending fighters to help the rebels.

Randa Slim of the New America Foundation.

RANDA SLIM: (Through Interpreter) Hezbollah until now has been able to sustain the kind of loyalty that it has enjoyed from its main constituency, meaning the Shiite of Lebanon, in times of war, like in 2006 and 2008, because they were able to convince those constituents that this was, in each case, a war of necessity.

FADEL: Against its traditional enemy: Israel. But now, she says, many Shiites are asking why Hezbollah is getting involved in a conflict that could hurt Lebanon.

SLIM: (Through Interpreter) I can hear these reservations now being voiced in Shiite majority areas, so there is now this shift of seeing Hezbollah's engagement in Syria as a war of choice and not necessity.

FADEL: Slim herself hails from the Shiite suburbs of Beirut. She has documented the deaths of at least 10 Hezbollah fighters over the last month, apparently in Syria. Families, she says, were instructed by Hezbollah not to speak about those deaths. But despite the gag order, Hezbollah is finding itself the subject of increasing scrutiny. Leila Fadel, NPR News, Beirut. Transcript provided by NPR, Copyright NPR.